How to check CPU clock speed in Linux

CPU clock speed refers to the number of cycles a CPU can execute per second. Previously, it was represented as a single number in MHz or GHz. However, with the introduction of boost clock speeds and multi-core CPUs, understanding CPU speed has become more complex. To gauge a CPU's speed, you'll need to know its minimum (base), maximum (boost), and current speed, as well as this information for all CPU cores.

It's important to note that clock speed is not an absolute indicator of a CPU's performance, as modern CPUs include numerous optimizations. A higher clock speed doesn't always guarantee better real-world performance.

Linux offers various tools to display CPU speed. Some are pre-installed on most systems, while others require manual installation. The level of detail provided by each tool may also vary.

1. Open the terminal.
2. Retrieve the CPU model to view the manufacturer's official speed from the product specifications.

   $ lscpu | grep ^Model\ name
   Model name:                      Intel(R) Core(TM) i7-10510U CPU @ 1.80GHz

   Related: How to check CPU information in Linux

3. Find the maximum speed of your CPU.

   $ sudo  dmidecode -t processor | grep "Max Speed"
     Max Speed: 4900 MHz

4. Check the current speed of your CPU.

   $ sudo  dmidecode -t processor | grep "Current Speed"
     Current Speed: 1683 MHz

5. Install additional tools for real-time monitoring if needed, such as auto-cpufreq on Ubuntu.

   $ sudo snap install auto-cpufreq # Ubuntu

6. Run the monitoring tool to see live frequency data for all CPU cores.

   $ sudo auto-cpufreq --monitor
   ##### snipped
   ------------------------------ Current CPU stats ------------------------------
   
   CPU max frequency: 4900 MHz
   CPU min frequency: 400 MHz
   
   Core  Usage Temperature Frequency
   CPU0:   0.0%     44 °C      900 MHz
   CPU1:   3.0%     43 °C     2300 MHz
   CPU2:   5.9%     43 °C     2477 MHz
   CPU3:   1.0%     42 °C     2300 MHz
   CPU4:   0.0%     44 °C     2300 MHz
   CPU5:   2.0%     43 °C      902 MHz
   CPU6:   1.0%     43 °C     2300 MHz
   CPU7:   0.0%     42 °C      900 MHz
   ##### snipped